I've done some buffer vs. image performance comparisions, the difference was always close to zero for me.
Images have the advantage that hardware can subdivide them to smaller tiles internally, so vertical pixels are closer in memory.
But for raytracing you probably don't get anything from that.
(Oops, Hodgman already mentioned this)
I'd use data sharing with OpenGL to avoid the need for another copy, although it's cost should not matter much as long as data stays on GPU.
It would be very slow if you download CL data to CPU, and upload it as GL texture again (but it's ok to do so to get going and care for such boring details later).
I would recommend to do some OpenCL vs. OpenGL compute shader tests as well if you want best performance, for both NV and AMD.
I expect OpenCL is still faster, but i'm not up to date.
Also see if you can use GLSL -> SpirV -> OpenGL. Might be a big difference as well, and i think there are already extensions for this.
In Vulkan i get very good performace (tested on AMD only), first time beating OpenCL with compute shaders.
However - on the API side, setting things up is frustrating with compute shaders.
I still prefer to develop everything with OpenCL and port working kernels to compute shader later.
So there is nothing wrong with focusing on OpenCL only, and later do some experiments with alternatives.